Presently, among the known epitaxial growth methods, the H—Si—Cl system CVD (chemical vapor deposition) process has been most widely studied and put in practical applications. The process is such that a silicon source gas is supplied by means of a hydrogen carrier onto a silicon substrate heated to an elevated temperature and a silicon single crystal is deposited and grown on the substrate through the reaction of the H—Si—Cl system. The common silicon source gases include SiCl4, SiHCl3, SiH2Cl2 and SiH4.
For the purpose of effecting such epitaxial growth, there have been used growth furnace apparatus of the type constructed so that a semiconductor substrate to be processed is held on a susceptor within a sealed chamber and a source gas is supplied into the chamber while heating the semiconductor substrate by a radiation heating system using halogen lamps or infrared lamps, for example. After the semiconductor wafer has been heated in a reference gas atmosphere e.g., hydrogen atmosphere within the chamber of the apparatus, a source gas is newly released into the reference gas and supplied onto the wafer surface so that a reaction gas consisting of a mixture of the reference gas and the source gas is produced and an epitaxial growth layer is formed on the wafer surface.
In this connection, the recent trend has been such that the size of reaction furnaces tends to become greater and bulky unavoidably due to the increase in the diameter of semiconductor wafers. As a result, the growth furnaces now in use for large-diameter wafers are generally of the single wafer processing type. Owing to the single wafer processing, this type has the effect of not only making the reaction chamber itself more compact but also simplifying the designing of heating conditions, gas flow distribution, etc., and ensuring higher uniformity of the epitaxial film characteristics.
While it is of course desirable that an epitaxial growth layer can be efficiently formed on the intended surface area of a semiconductor wafer, in fact the deposition of reaction product can occur on the surface of all the objects which contact with a source gas within the chamber. Such deposition of reaction product on the undesired portions tends to become an obstacle to the production of high-quality wafers.
Particularly, if such reaction product is caused to deposit on the moving parts of a wafer holding mechanism around a semiconductor wafer, there is the danger of the product peeling off and falling on the wafer surface due to the movement of these parts thereby causing particle contamination.
Also, if the source gas is allowed to flow around from the border of the semiconductor wafer to the back side of the wafer, not only there is the danger of an epitaxial growth layer being formed on the wafer back side, but also there is the possibility of the product being deposited on a heating mechanism arranged on the back surface side and causing variations in the amount of heating on the wafer during the epitaxial growth reaction thereby deteriorating the quality of the wafer.
In view of the foregoing deficiencies, it is an object of the present invention to provide an epitaxial growth furnace equipped with at least one semiconductor wafer holding mechanism capable of preventing the deposition of a reaction product which is a cause of particle contamination on the surface of a semiconductor wafer. It is another object of the present invention to provide an epitaxial growth furnace equipped with at least one semiconductor wafer holding mechanism capable of preventing a source gas from flowing around from the border of a semiconductor wafer to its back surface side.